Conservation and conversion of poultry waste products

ABSTRACT

Poultry feces are processed through a digester and a separator to produce undissolved solid material and a liquid filtrate. The solid material contains primarily food undigested by the poultry which is blended with comminuted egg shells, comminuted feathers, nutrients to provide a balanced food and new food to produce feed for fowl or stock. The filtrate is chemically treated for recovery of uric acid precipitate, and the remaining filtrate is used as a bacterial culture to produce bacterial protein. Used liquid from the bacterial culture is used as hydroponic culture to grow green fodder.

This application is a continuation-in-part of application Ser. No.207,488, filed Dec. 13, 1971 and now abandoned, for Conservation andConversion of Poultry Waste Products.

The present invention relates to a process for conserving food valuefrom poultry waste products and for converting nonfood components intocultures utilized in the production of additional food, plus therecovery of chemical by-products.

More specifically, it is an object to utilize poultry waste products inthe form of feces, egg shells and feathers for the maximum production offood products which can be utilized by such poultry and thereby reduceto the maximum extent the cost of feeding such poultry.

A further object of the invention is to recover and produce food frompoultry waste products by the use of equipment and procedures which arepractical and economical, which minimize unpleasant processingconditions and which equipment and procedures can process the materialautomatically and with minimum monitoring supervision and control.

An important object of the present invention is to minimize the problemof disposing of poultry waste products by conserving and converting theminto useful products.

The drawing is a flow diagram representing sequential steps in theconservation and conversion process of the present invention.

The process of the present invention is particularly well suited to theconservation and conversion of waste products from chickens, but is alsoapplicable to the utilization of waste products of poultry of othertypes. A principal function of the process is to recover undigested foodfrom poultry feces for reuse as food. It has been found that as much as80 per cent of the dry weight of poultry feces is composed of undigestedfood.

Poultry digests and utilizes approximately 80 per cent of the dry weightof food eaten. Feces excreted are approximately 75 per cent water, andof the 25 per cent dry material of the feces 80 per cent is undigestedfood. The purpose of the present invention is to recover such 80 percent of the undigested 20 per cent of the original food, amounting toapproximately 15 per cent to 16 per cent of the original food, and toutilize it as a refeeding ingredient. To recover, and thus conserve,such undigested food from poultry feces, the feces are first comminutedin a grinder-blender 1.

After being reduced to a substantially homogeneous condition, thecomminuted material is transferred to a digester 2 in which water andbase, such as alkali are added to the comminuted material. Theproportion of water to comminuted material should be from one to threetimes as great a volume of water as of comminuted material, butpreferably the ratio should be approximately equal volumes of water andcomminuted material. The base can be of the organic or inorganic type,depending upon which type may be preferable for ultimate use of theliquid phase of the material. Potassium hydroxide and/or sodiumhydroxide alkalis are suitable. The concentration of alkali may bewithin the range of 1 to 4 per cent of the weight of water,approximately 2 per cent being preferable. The principal purpose of thebase solution added in the digester is to neutralize the acidity of thefeces, to assist in solution of soluble ingredients of the feces and todisinfect the feces. The operation of the digester is conducted withoutthe addition of heat other than that supplied by the base, thetemperature being in the range of 60° F. to 90° F. The purpose of thedigesting process is to dissolve from the comminuted feces all materialwhich is soluble in the aqueous base solvent to produce a liquid phaseand a solid phase.

The contents of the digester should be stirred continuously during thedigesting process so as to bring all of the solid material into intimatecontact with the treating liquid. Also, to facilitate such contact thefeces should be ground so that at least most of the particles are lessthan one millimeter in maximum dimension. The digestion process shouldbe accomplished in approximately fifteen minutes. The degree ofdigestion of the material will depend upon its composition, but thedigestion should be sufficient so that the solid material recovered forfood purposes does not have a disagreeable odor or appearance. From thedigester, the digested material is transferred to a separator 3, bywhich the solid phase and the liquid phase are separated by settling,centrifuging, filtration, dializing or some combination of suchoperations.

The liquid phase of the separation includes soluble protein, inorganicsalts, uric acid, bacterial products, and mucin. The separated solidmaterial to be recycled as food enters the drier 4 in which excessmoisture is removed. At the same time the material preferably issubjected to a temperature sufficiently high to sterilize it by killingbacteria.

It has been found that the food thus recovered from poultry feces mayhave a composition including 58 per cent of organic material and 42 percent of inorganic material.

Such food may also contain:

    Fiber                   10.7%                                                 Fat                     0.5                                                   Carbohydrate            14.0                                                  Protein (based on N)    5.8                                                   Nitrogen                0.95                                                  Phosphate               1.9                                               

The amino acid content of the recovered food may be:

    Isoleucine           0.80%                                                    Leucine              1.3                                                      Lysine               0.51                                                     Histidine            0.20                                                     Valine               1.1                                                      Threonine            6.0                                                      Glycine              10.3                                                     Arginine             0.42                                                     Methionine           0.024                                                    Cystine              0.053                                                    Phenylalanine        0.087                                                    Tyrasine             0.0040                                               

The content of the last four components is inadequate and may besupplemented by adding nutrients as discussed below.

Food material is obtained not only by recovering undigested food fromthe feces, as described above, but the calcium necessary for poultrydiets can be supplied in the form of comminuted egg shells. Comminutedfeathers can also be used as a souce of protein. The feathers could becooked as well as ground, so that the protein feather component would bein the form of hydrolyzed feather meal, such as disclosed in Brown etal. reissue Pat. No. Re.25,138. To render the feed more palatable, it isdesirable to mix it with a greater or lesser proportion of new fooddepending upon the type of fowl or stock to be fed, and the desiredcharacteristics of the feed.

The final food product is therefore produced by combining in a blender 5the dried undigested food recovered in the drier 4 from the poultryfeces, egg shells comminuted in a grinder 6, feathers comminuted in agrinder 7 and new, uneaten food and such nutrients as may be required toproduce a nutritionally balanced feed. It will be understood that theproportions of the various feed components can vary widely dependingupon the requirements of the fowl or stock, and the personal preferenceof the farmer. It is intended that the process of the present inventionbe conducted at the chicken farm so that the food salvaged from thefeces will be most conveniently available to be used again. The eggshells available will depend on to what extent the chicken farmprocesses the eggs into bulk raw eggs or into powdered eggs and to whatextent chickens are processed and plucked to provide feathers that canbe mixed with the recovered food.

The amount of the recovered food preferably is in the range of 10 percent to 20 per cent by weight of the final feed and ordinarily is about15 per cent by weight. The egg shells and feathers may be from 5 percent to 10 per cent by weight of the food so that the total foodproducts recycled would be from 15 per cent to 30 per cent of thepoultry or stock feed by weight, representing a corresponding saving innew food required.

The liquid phase of the separation in the separator 3 may remove varioustypes of chemicals that can be used as a source of chemical by-products,and can also provide nutrient liquid for bacterial cultures and/orhydroponic cultures. The remaining liquid phase is transferred from theseparator 3 to the reagent blending tank 8 to which suitable reagentsare supplied for the purpose of producing uric acid. Such uric acidproduction may, for example, be of the type disclosed in U.S. Pat. No.2,302,204 of Gable.

Following the blending of the liquid phase from the separator 3 and thereagents in the reagent blending tank 8, the mixture is transferred tothe settling tank 9 in which the uric acid is precipitated and settles.Such settled material is transferred to the washer-drier 10 from whichthe uric acid is removed in powder form.

The uric acid by-product of the feces may be from 2 per cent to 10 percent of the fecal dry weight source material. The uric acid can beprocessed subsequently to produce a variety of drugs, chemicals,plastics and adhesives including cyanuric acid, from which melamine canbe produced for use in making melamine resin plastic. In addition, theuric acid can be used in the production of barbituric acid, dialuricacid, violuric acid, alloxantin, alloxan, parabanic acid, biuret,purpuric acid, hydurilic acid, allantoic acid, allantoin and urea.

In addition, other chemical products can be recovered from the liquidphase of the digested feces resulting from the separation in theseparator 3, such as plant hormones, steroids, ureido compounds, aminoacids, carbohydrates and biliverdin. Some of the amino acids may besuitable for adding to the blender 5 for balancing the nutrient value ofthe fowl or stock feed produced in the blender.

Liquid drawn from the settling tank 9 can be used as a source of carbon,nitrogen, sulphur, nutrient chemicals and minerals and/or used inbacterial cultures and/or hydroponic cultures. Bacterial protein may beproduced by such bacterial cultures and green fodder can be produced byhydroponic cultures which can be used as additional food or foodingredients for fowl or stock feed. A representative utilization of suchliquid is indicated in the drawing.

Liquid can be transferred from the settling tank 9 to a bacterialculture 11, and such liquid can be supplemented by spent respirationgases which are principally carbon dioxide and nitrogen. Modern poultryhouses have completely controlled air-conditioning systems in which theair is recirculated. During such recirculation the temperature andhumidity of the air is adjusted. Such air can be bubbled through thebacterial culture and the hydroponic culture to dissolve from it carbondioxide and other soluble gases for utilization by the bacteria andplants supported by such cultures. Such a culture can produce about 1gram of bacterial protein for 8 liters of liquid. Such bacterialcultures may, for example, be similar to those disclosed in U.S. Pat.No. 2,742,359 of Rahn, U.S. Pat. No. 3,421,942 of McBaine, or U.S. Pat.No. 3,462,275 of Bellamy.

The resulting bacterial protein can be dried, preferably sterilized, andadded to the blender 5 as a part of the new food and balancing nutrientcontent of the poultry or stock feed. Drying can be effected by heatingor centrifuging, or both. The mixture of amino acids in the bacterialprotein could be fractionated to recover specific acids if desired.Alternatively the entire mixture could be freeze-dried. After drying theentire mixture could be pelletized to provide a high grade protein forpoultry or stock feed.

Alternatively, or after being used as the liquid for the bacterialculture, the liquid can be used for a hydroponic culture 12 in which togrow green fodder such as duckweed and/or barley. Such hydroponics maybe generally of the type disclosed in U.S. Pat. No. 2,952,096 of Hughesor U.S. Pat. No. 3,292,584 of Brodrick. The culture liquid will supplythe plant life with potash, phosphorus, ammonia, sulphur and mineralsobtained from the poultry feces. For proper plant growth the inorganicsalt content of the culture should not appreciably exceed 3 per cent byweight of the culture. The liquid discarded from the hydroponic cultureis sufficiently degraded so that it will not cause appreciable pollutionif discharged without treatment into natural bodies of fresh water.

The composition of poultry feces resulting from feeding the poultry witha predetermined food composition is substantially constant. Consequentlythe solid phase of the material recovered from the separator 3 issubstantially uniform, and if it is mixed with predetermined proportionsof comminuted egg shells, comminuted feathers, new food, and perhapsbacterial protein, the composition of the food fed to the poultry willbe substantially unvarying. It will therefore not be necessary tomonitor the operation of the process closely or to provide constantsupervision or frequent adjustment of the operation of the process.

I claim:
 1. The method of producing a composite fowl or stock feed whichcomprises comminuting poultry feces, mixing aqueous base liquid with thecomminuted poultry feces for dissolving from the feces componentssoluble in such aqueous base liquid, separating the solid phase and theliquid phase of the resulting material, and blending with other foodcomponents such solid phase of the material containing food undigestedby the poultry.
 2. The method defined in claim 1, including addingcomminuted egg shells to the solid phase of the resulting material andblending such solid phase and such comminuted egg shells.
 3. The methoddefined in claim 1, including adding comminuted feathers to the solidphase of the resulting material and blending such solid phase and suchcomminuted feathers.
 4. The method defined in claim 1, in which theaqueous base liquid is alkaline liquid.
 5. The method of producing acomposite fowl or stock feed which comprises comminuting poultry feces,agitating a mixture of aqueous base liquid and such comminuted poultryfeces for dissolving from the feces components soluble in such aqueousbase liquid, separating the solid phase and the liquid phase of theagitated mixture, heat-drying and simultaneously sterilizing theseparated solid phase, and blending with other food components suchsolid phase containing food undigested by the poultry.
 6. The methoddefined in claim 5, in which the aqueous base liquid is alkaline liquid.